As far as M/M goes, I wouldn't be surprised if armourers didn't use parts from one set to repair or complete another, particularly when dealing with items in limited issue like sniper equipments. I would expect though, that serial numbers would be changed, to demonstrate that the pieces had been properly fitted together. When these vintage sniper rifles were in service, I am sure that budgets were rather frugal, and servicable equipment would have been retained and reused, rather than being replaced. This isn't a comment about Swedish practices, but I would suspect that there would be little difference from nation to nation. Problem is that sniper sets have escalated dramatically in value, and it can be worthwhile to assemble bits into complete units. Look at all the recently assembled MNs in the US.